Welding is a well-established method to connect components of weldable material, as for example steel, to each other. Exemplary welding methods are the resistance spot welding and the stud welding, at which two oppositely arranged components are connected to each other selectively or point by point by means of welding. A further welding method is the stud welding with light arc.
Nowadays, in different industrial sectors, components have to be connected to each other which consist of partly non- or poorly weldable material. Nevertheless, welding provides an effective connection method even for these components of non- or poorly weldable material. For this purpose, a welding auxiliary joining part of weldable material is fastened in the component of non- or poorly weldable material. Subsequently, a welding connection between a component of weldable material and the welding auxiliary joining part is produced so that the component of weldable material and the component of non- or poorly weldable material are connected to each other by means of the welding auxiliary joining part. Examples for components of non- or poorly weldable material are aluminum sheets, moldings of plastic or fibre-reinforced plastic, for example carbon fibre-reinforced plastic, to mention only a few examples. The above-described method for example follows from the German patent application DE 100 15 713 A1.
A connection method by means of welding between a component of non- or poorly weldable material and a component of weldable material is described in the German patent application 10 2005 006 253 A1. Here, a stud having a shank and a head of weldable material is inserted into a pre-fabricated hole in the component of non- or poorly weldable material and is subsequently welded to the component of weldable material. For reliably fastening the stud with its shank in the pre-punched portion of the component of non- or poorly weldable material, the shank of the stud is deformed laterally after the welding by means of compression so that a force-fit connection between the shank of the stud and the inner wall of the hole of the component results. Due to the plurality of method steps, the here described connection method is technically complex and time-intensive.
In the German patent applications DE 10 2004 025 492 A1 and DE 10 2007 036 416 A1, rivets, studs or nails are set as welding auxiliary joining part into components of non- or poorly weldable material, respectively. The tip of the welding auxiliary joining part protrudes from the one side of the component of non- or poorly weldable material and forms a welding spot having a very small contact surface for contacting the opposing component of weldable material. As soon as the welding auxiliary joining part and the component of weldable material are connected to each other, for example by means of resistance welding in the manner of the resistance spot welding or the resistance stud welding, the tip or edge of the welding auxiliary joining part is melted so that a so-called welding lens or weld nugget is formed. Due to the small contact surface between the welding auxiliary joining part and the component of weldable material at the tip or in the edge portion of the welding auxiliary joining part, the contact zone for welding is relatively small. This prolongs the welding procedure or worsens the welding connection due to the small contact surface compared to oppositely arranged components which contact each other in a greater portion. Corresponding to the small contact surface between welding auxiliary joining part and the component of weldable material, the forming weld nugget is small. This affects among others the mechanical loadability as well as the lifetime of the connection produced. Further, and when using a half-hollow punch rivet as welding auxiliary joining part, a waste slug of non- or poorly weldable material is produced. At the subsequent welding, this waste slug is arranged in the welding zone and in the portion of the weld nugget so that the emerging welding connection is affected in its quality due to this contamination.
Further, in DE 10 2004 025 492 A1, it is described as advantageous to mechanically deform the component of weldable material in the contact portion for the later welding by means of the setting procedure of the welding auxiliary joining part in the component of non- or poorly weldable material. Particularly, a tip or an edge of the welding auxiliary joining part enters the component of weldable material or creates a dent or recess in this component of weldable material. This dent shall then facilitate the formation of a sufficiently large weld nugget during the resistance welding between the welding auxiliary joining part and the component of weldable material in the portion of this depression or dent, respectively. For realizing this method, it is, however, necessary to arrange all components to be connected above each other before the welding auxiliary joining part is set. Otherwise, an additional work step is necessary for creating the dent in the component of weldable material and aligning it with respect to the welding auxiliary joining parts already set. This is complex, time intensive and requires further an additional constructive effort for precisely positioning the components to be connected to each other and is limited in the choice of the possible welding methods and the process-sequence.
DE 100 60 390 A1 describes a punch rivet method at which a punch rivet is driven through a first electrically non-conductive material, as for example plastic, by means of an electrode punch and is connected to a second electrically conductive material lying on an electrode matrix or die. Electrode punch and electrode die are connected to opposite poles of a voltage source. As soon as the punch rivet has penetrated the first material and is in contact with the second electrically conductive material, a current flow through the punch rivet occurs. As the punch rivet is heated due to the current flow, the further joining process of the punch rivet is facilitated. As in the here described punch rivet method, hollow, half-hollow or solid rivets are used, the punch rivet drives waste material in front of it through the first electrically non-conductive material during its joining process. This waste material hinders an electrical contact between punch rivet and second material and thus the current flow through the punch rivet. Further, it is disadvantageous that the punch rivet penetrates the electrically non-conductive material in the cold state which leads to crack formation and other failure mechanisms especially in brittle plastics and similar materials.
DE 10 2010 020 569 A1 describes a thermal joining of a first electrically non-conductive component to a second electrically conductive component based on an electrical heating. To this end, first a joining auxiliary means consisting of an electrically conductive material is formed into the electrically non-conductive component. In an installation process prior to the connection method, the joining auxiliary means is fastened in the first component by means of rolling, stamping, die forming, pushing in, embossing or gluing. The joining auxiliary means provides the electrically conductive abutment contact for the subsequent electrical-thermal welding with the second component. For this purpose, the first component having the joining auxiliary means and the second component are positioned between an electrode punch and an electrode die which are arranged opposite to each other. An electrical current flow through the joining auxiliary means and the electrically conductive second component between electrode punch and electrode die leads to a welding between the joining auxiliary means and the second component at the boundaries abutting each other. Also, the thermal joining method described here has its disadvantages in that first of all, and in a prior method, an auxiliary joining means has to be fastened in the first component of electrically non-conductive material. Therefore, several steps of processing the auxiliary joining means and the first component are necessary at this point before the first component and the second component between electrode punch and electrode die may be connected to each other.
It is thus an object of the present invention to provide a less time consuming connection method between at least a component of non-weldable material and at least a component of weldable material compared to the prior art.